Polishing head and polishing processing device

ABSTRACT

A pressing mechanism of a polishing head includes a first pressing body configured so as to include a first airbag and a first pressure disc formed so that a portion near the center of a contact surface which comes into contact with an elastic body is convex-shaped towards the elastic body; and a second pressing body, which is formed as a cylinder having the first pressure disc disposed on the inner circumferential side thereof, and which is configured so as to include a second airbag and a second pressure disc formed so that a portion near the outer edge of a contact surface which comes into contact with the elastic body is concave-shaped towards the elastic body.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a polishing head and a polishing processing device for polishing to planarize a substrate such as a semiconductor wafer, a glass substrate and the like.

In recent years, in a manufacturing process of semiconductor devices, along with high integration of substrates, technology to planarize a substrate surface has become more and more important. Chemical Mechanical Polishing (CMP) is the most important technology among the planarizing technology. In the CMP process, a polishing processing device (also referred to as a polishing device) is used to supply polishing solution including abrasive grains of silica (SiO₂) etc. on a polishing surface such as a polishing pad while slidably bringing the substrate into contact with the polishing surface to perform the polishing processing.

In such a polishing processing device, if relative speed and pressing pressure between a surface of the substrate subject to the polishing processing (hereinafter referred to as “surface to be polished”) is not uniform over the entire surface of the surface to be polished, polishing unevenness, polishing insufficiency, or excessive polishing is caused. Moreover, since the polishing pad has low elasticity, non-uniform pressing force may be applied to a portion near an outer peripheral end of the substrate. This may cause a roll-off condition in which only the portion near the outer peripheral end of the substrate is excessively polished. It is noted that, an attempt is being made to uniformly apply the pressing force over the entire surface of the substrate by forming a holding surface of the substrate with an elastic film (also referred to as membrane) consisting of a low elastic material such as rubber, etc. and applying pressure fluid such as air pressure to a back surface of the elastic film.

An evaluation index of flatness of a substrate surface (flatness evaluation index) includes Global Backsurface-referenced Ideal plane/Range (GBIR), Site Frontsurface-referenced least sQuares/Range (SFQR) etc. GBIR is a global flatness index in which backsurface is used as a reference, and it is used for evaluation of flatness concerning an entire wafer surface defined except a peripheral edge portion. GBIR is defined as a width of a deviation between maximum and minimum thicknesses of a front side of a semiconductor wafer relative to a reference surface when a back side of the semiconductor surface is determined as a reference surface. SFQR is a frontsurface-referenced site flatness index, and it is evaluated in accordance with each site. SFQR is defined as a range of positive and negative deviations from a reference surface when a cell having an arbitrary dimension (e.g., 26 mm*8 mm) is determined on a surface of a semiconductor wafer and a surface obtained by the method of least square in regard to this cell surface is determined as the reference surface. Further, a value of SFQRmax represents a maximum value of SFQR in each site on a predetermined wafer. A polishing processing device capable of performing polishing processing of high flatness represented by these flatness evaluation indexes is required.

In view of equalizing polishing amount of the substrate, there is a wafer polishing device disclosed in a patent document 1. In the wafer polishing device, a wafer is held in a condition that an outer peripheral portion of the wafer can be elastically deformed in a wafer thickness direction while performing polishing. Thereby, if a contact pressure with the polishing pad against the outer peripheral portion of the wafer increases, the outer peripheral portion of the wafer is elastically deformed in a direction escaping from the polishing pad in accordance with the contact pressure. As a result, excessive polishing of the outer peripheral portion of the wafer is prevented.

Patent document 2 discloses a semiconductor wafer. To meet a plurality of flatness evaluation indexes, on the assumption that polishing unevenness or polishing insufficiency occurs, a semiconductor wafer is formed in advance in a shape predicting the occurrence of the polishing unevenness or polishing insufficiency.

CITATION LIST Patent Literature

Patent Literature 1: JPH08-257893;

Patent Literature 2: JP2012-231005

SUMMARY OF INVENTION Technical Problem

With the wafer polishing device as disclosed in the patent document 1, due to the elastic deformation, excessive polishing of the outer peripheral portion of the wafer is relaxed, indeed. However, conventional polishing processing is simply performed to the rest of the wafer polishing portions. Thereby, GBIR and SFQR at particular portions on the surface to be polished cannot be enhanced, which is a problem.

Further, with the semiconductor wafer as disclosed in the patent document 2, with a particular polishing processing device, polishing processing needs to be performed. Further, polishing condition may be changed depending on operation state of the polishing processing device. Also, even in the polishing processing devices of the same type, each device may have its own “characteristics”. It is necessary to cope with such matters, which is also a problem.

The main object of the present invention is to provide a polishing processing device and its component capable of preventing the occurrence of polishing unevenness, polishing insufficiency, or excessive polishing of the surface to be polished of the substrate. Further, a polishing processing device and its component, capable of enhancing GBIR and SFQR of the substrate surface by applying predetermined pressing force over the entire surface of the surface to be polished of the substrate, are provided.

Solution to Problem

According to the present disclosure, there is provided a polishing head to solve the problems as mentioned. The polishing head which is provided in a polishing processing device having a polishing surface which horizontally rotates, comprises: a holding mechanism configured to hold a substrate to be subjected to polishing processing in such a manner that a surface to be polished of the substrate is slidably brought into contact with the polishing surface; and a pressing mechanism configured to press the substrate held by the holding mechanism from a rear surface side of the surface to be polished toward the polishing surface, wherein the pressing mechanism comprises a pressing body, an elastic body disposed to come into contact with the pressing body, and a fluid supply mechanism configured to supply the pressure fluid to the pressing body, wherein the pressing body is configured such that pressure fluid is sealed to the pressing body to generate pressing force in accordance with quantity of the pressure fluid toward the rear surface side of the substrate, wherein the pressing body comprises a first pressing body which is cylindrically-shaped and a second pressing body which is annularly-shaped disposed to surround the first pressing body, wherein the first pressing body is formed so that a portion near a center of a contact surface which comes into contact with the elastic body is convex-shaped toward the elastic body side, and the second pressing body is formed so that a portion which is outer peripheral side of the contact surface which comes into contact with the elastic body is convex-shaped toward the elastic body side, and wherein the pressing force, generated by the pressure fluid sealed in the first pressing body and the second pressing body separately and respectively, is respectively applied to the rear surface side of the substrate held by the holding mechanism through the elastic body.

Further, the polishing processing device comprises: a polishing table having a circular or generally circular polishing surface, a polishing head configured to hold a substrate to be subjected to polishing processing to slidably bring a circular surface to be polished of the substrate into contact with the polishing surface, and a driving mechanism configured to horizontally rotate at least one of the polishing head and the polishing table, wherein the polishing table is configured such that a radius of the polishing surface is larger than a diameter of the surface to be polished of the substrate, wherein the polishing head comprises: a holding mechanism configured to hold the surface to be polished of the substrate to be slidably brought into contact with the polishing surface, a pressing body, in which pressure fluid is sealed to generate pressing force in accordance with quantity of the pressure fluid toward the rear surface side of the substrate, an elastic body disposed to come into contact with the pressing body, and a fluid supply mechanism configured to supply pressure fluid to the pressing body, wherein the pressing body comprises a first pressing body which is cylindrically-shaped and a second pressing body which is annularly-shaped disposed to surround the first pressing body, wherein the first pressing body is formed so that a portion near a center of a contact surface which comes into contact with the elastic body is convex-shaped toward the elastic body, wherein the second pressing body is formed so that a portion which is outer peripheral side of the contact surface which comes into contact with the elastic body is convex-shaped toward the elastic body side, and a pressing mechanism configured to respectively apply the pressing force, generated by the pressure fluid sealed in the first pressing body and the second pressing body separately and respectively, to the rear surface side of the substrate held by the holding mechanism through the elastic body.

Effect of Invention

According to the polishing head of the present disclosure, in the polishing processing device, it is possible to apply desired pressing force over the entire surface to be polished of the substrate through the elastic body without any discontinuous part. This prevents polishing unevenness, polishing insufficiency, or excessive polishing caused by excess or deficiency of the pressing force. Thereby, it is possible to further enhance GBIR and SFQR of the substrate surface.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of the polishing processing device according to a first embodiment.

FIG. 2 is a diagram illustrating one configuration example of a polishing head according to the first embodiment.

FIG. 3 is a schematic longitudinal sectional view of the polishing head.

FIG. 4 is a diagram for explaining occurrence of buckling twist.

FIGS. 5A and 5B are longitudinal sectional views for explaining the distribution of pressing force applied to the substrate when conventional polishing head is used.

FIGS. 6A, 6B and 6C are diagrams for explaining mechanism when the surface to be polished of substrate W is formed in an omega (□□ shape in the polishing processing using a general polishing head.

FIGS. 7A and 7B are diagrams for explaining the distribution of pressing force by the polishing head according to the first embodiment.

FIGS. 8A to 8C are diagrams for explaining connection of a lid body and a top ring through a drive pin.

FIGS. 9A and 9B are diagrams for explaining that polishing pressure of the substrate end portion changes due to difference of how an elastic film is adhered.

FIGS. 10A to 10F are diagrams for explaining impact on flatness of the substrate end portion caused by difference of how the elastic film is adhered and fixed to the top ring.

FIGS. 11A to 11C are diagrams for explaining, following FIGS. 10A to 10 F, influence on the flatness of the substrate end portion caused by difference of how the elastic film is adhered and fixed to the top ring.

FIG. 12 is a diagram for explaining entire procedure of a polishing processing method performed in the polishing processing device.

FIGS. 13A to 13C are diagrams showing one configuration example of a polishing head according to a second embodiment.

DESCRIPTION OF EMBODIMENTS

In the following, embodiments of the present invention are described with reference to the drawings. Here, present inventors have found following features through detailed study. In particular, in the polishing processing using a general polishing processing device, (1) a profile of the substrate surface (surface to be polished) is tend to be formed in an omega shape, which is described later; (2) polishing disturbance expresses due to rotating buckling of membrane at the top ring. The present inventors have found that the profile, omega-shaped, and the expression of the polishing disturbance are factors which deteriorate the evaluation result of GBIR and SFQR. At the same time, the present inventors have solved the factors expressed. The fact that the surface to be polished is omega-shaped means that the portions near the center and the outer peripheral of the surface to be polished are convex-shaped as compared to the other portions. It is noted that a state in which the outer peripheral portion of the substrate is convex-shaped may be referred to as “rising” of the outer peripheral portion of the substrate. The present inventors have also found that, due to inner disk buckling (in-plane buckling) phenomena of the substrate itself at the time of the polishing processing, the surface to be polished is omega-shaped. Although details will be described later, the substrate, which is pressed by the polishing pad and is being rotated at the time of the polishing processing, is controlled its popping out in an outer direction by a retainer ring. Thereby, it has been found that in-plane force is applied to the substrate in a plane direction (a direction perpendicular to a rotation axis of the substrate) and the in-plane buckling occurs by a reaction force with the retainer ring. In the following, based on these findings, a description is provided with regard to the polishing processing device capable of enhancing GBIR and SFQR.

In the polishing processing device of the present embodiment, substrate subject to the polishing processing is a semiconductor wafer, a glass substrate etc. In the present specification, one surface of the substrate, which is circular or generally circular, is a surface to be polished. The polishing processing device comprises a polishing table and polishing head. On the polishing table, a polishing pad as a polishing material is adhered. The polishing table is to horizontally rotate the polishing pad. The polishing head is to face and slidably bring the surface of the substrate to be polished into contact with the polishing pad. The substrate is pressed to the polishing pad by the polishing head. Then, by rotating at least one of the polishing table and the polishing head while supplying polishing solution (slurry) to the polishing head, polishing processing is performed on the surface to be polished. In the following, embodiments of the polishing processing device will be described.

First Embodiment

FIG. 1 is a schematic configuration diagram of a polishing processing device 1. The polishing processing device 1 as shown in FIG. 1 comprises a polishing head 13 which holds a substrate W to press its surface to be polished to a polishing pad 12 which is adhered on a surface portion of the polishing table 11. In addition, the polishing processing device 1 comprises a nozzle N for supplying the polishing solution toward the polishing pad 12, a motor (illustration omitted) for horizontally rotating the polishing table 11 and the polishing head 13 respectively, a polishing solution supply mechanism (illustration omitted) which is connected to the nozzle N, and a control unit 20 including a computer for controlling each driving unit including the motor.

The polishing pad 12 is disk-shaped. Its radius is larger than a diameter of the surface to be polished of the substrate W. In this mechanism or arrangement, the rotation number and a rotation direction of the polishing pad 12 and the polishing head 13 can be changed so that relative polishing speed in the surface of the substrate W can be adjusted. The polishing pad 12 may be materials available on the market including those consisting of non-woven fabric, foamed urethane etc., as long as the materials are elastic.

The polishing head 13 comprises a holding mechanism (e.g., unit or means) and a pressing mechanism. The holding mechanism holds or maintains the substrate W such that its surface to be polished is slidably brought into contact with the polishing pad 12. The pressing mechanism presses the substrate W held from a rear surface side of its surface to be polished toward the polishing pad 12. Details of these mechanisms will be described later.

The control unit 20 mainly performs followings: (1) to position the nozzle N; (2) to control start or stop supplying the polishing solution from the nozzle N; (3) to control supply amount of the polishing solution which is jet and supplied from the nozzle N, and (4) to control start or stop of the motor etc. Rotating force of the motor controlled by the control unit 20 is transmitted to the polishing table 11 through a driving unit (not shown). As a result, the polishing table 11 rotates horizontally or rotation is stopped.

The rotating force of the motor is also transmitted to the polishing head 13 through a driving unit such as a universal joint (not shown). Due to this, the polishing table 11 rotates horizontally or rotation is stopped. In general, the polishing table 11 and the polishing head 13 rotate in the same direction. This is because if the polishing table 11 and the polishing head 13 rotate in a reverse direction each other, the polishing may be non-uniform. Even rotating in the same direction, by adjusting the rotation speed, polishing accuracy can be enhanced. It is noted that, in one case, the rotation force of a single motor may be transmitted to the polishing table 11 and the polishing head 13 via a gear respectively having different gear ratio. In another case, for each of the polishing table 11 and the polishing head 13, the rotation force is separately provided via respective motor. One skilled in the art may arbitrarily determine which case is to be designed. Control procedures executed by the control unit 20 will be described later.

The polishing solution is supplied toward the polishing pad 12 from the nozzle N for a predetermined time period in a state in which the rotation speed of the polishing table 11 has reached a predetermined value by the control of the control unit 20.

[Polishing Head]

Next, a description is provided in detail with regard to a configuration of the polishing head 13 which is provided in the polishing processing device 1. FIG. 2 is a diagram illustrating one configuration example of the polishing head 13. The polishing head 13 as shown in FIG. 2 comprises an air pipe AP, a lid body 131, a first airbag 132, a ring-shaped second airbag 133, a first pressure disk 134, a ring-shaped second pressure disk 135, a top ring 136, an elastic body 137, an elastic film 138, a template back film 139 (hereinafter referred to as a back film 139), and a template retainer ring 140 (hereinafter referred to as the retainer ring 140).

Four arms AMs are respectively disposed at equal intervals near the outer peripheral end of a lower bottom surface of the lid body 131. A drive pin D1 is disposed near an end portion of the arm AM which is opposite to the end portion which comes into contact with the lower bottom surface of the lid body 131. A pair of drive pins D2 is respectively disposed on the first pressure disk 134 on both side surfaces in its radial direction. It is noted that a combination of the first airbag 132 and the first pressure disk 134 is a first pressing body. A pair of drive pins D3 is respectively disposed on the second pressure disk 135 on both side surfaces in its radial direction. Further, a drive pin groove G2, having an opening on its upper bottom surface and inner surface side, is provided on the second pressure disk 135. The drive pin groove G2 is formed in a size which allows the drive pin D2 to be freely inserted and removed from the upper bottom surface side of the second pressure disk 135. It is noted that what combination of the second airbag 133 and the second pressure disk 135 is a second pressing body.

A drive pin groove G1, having an opening on its upper bottom surface side and inner surface side, is provided on the top ring 136. The drive pin groove G1 is formed in a size which allows the arm AM with the drive pin D1 to be freely inserted and removed from the upper bottom surface side of the top ring 136. Also, a drive pin groove G3, having an opening on its upper bottom surface side and inner surface side, is provided on the top ring 136. The drive pin groove G3 is formed in a size which allows the drive pin D3 to be freely inserted and removed from the upper bottom surface side of the top ring 136. It is noted that the drive pins D1, D2, and D3 comprise a bearing such as ball bearing, roller bearing etc.

The air pipe AP is connected to a fluid supply mechanism (not shown). One air pipe AP supplies pressure fluid (for example, compressed air) toward the first airbag 132 consisting of a flexible material. Alternatively, it becomes a fluid passage for recovering the pressure fluid supplied from a first pressure chamber. The other the air pipe AP supplies the pressure fluid toward the second airbag consisting of the flexible material. Alternatively, it becomes the fluid passage for recovering the pressure fluid supplied from a second pressure chamber. The pressure fluid is separately and respectively sealed in each airbag. Then, the airbag expand. With the expansion of the airbags, in accordance with the quantity of the pressure fluid sealed, processing pressure for pressing the substrate W is generated. It is noted that, through the control by the control unit 20, the pressure fluid is supplied or the pressure fluid supplied is recovered. In the following, a description is provided in detail with regard to each configuration with reference to FIG. 3.

FIG. 3 is a schematic longitudinal sectional view of the polishing head 13. Generally, the polishing head 13 comprises the holding mechanism, the pressing mechanism, and a torque transmission mechanism.

[Holding Mechanism]

The holding mechanism controls popping out of the substrate W, which is energized by the rotation force of the polishing table 11 and the polishing head 13, toward an outer peripheral direction. The holding mechanism faces (contacts) and slidably brings the surface to be polished of the substrate W into contact with the polishing pad 12. With this state, the holding mechanism holds such that the center axis of the substrate W matches its rotation axis. In particular, the holding mechanism comprises the retainer ring 140 comprising a holding surface which comes into contact with the outer end portion of the substrate W and a positioning surface which comes into contact with the polishing surface. The holding mechanism also comprises the back film 139 (not shown in FIG. 3) which comes into contact with the rear surface of the surface to be polished of the substrate W. To surround the outer peripheral of the substrate W, the retainer ring 140 is positioned on an outer bottom surface of the elastic film 138 and holds an outer peripheral end of the substrate W by a surface contact. The back film 139 is a film-like thin film which is stretched on the retainer ring 140. For example, as compared to a case in which the retainer ring 140 is used without the back film 139, ringing at the time of polishing is easily held by using the back film 139. Also, when the polishing is finished, with the back film 139, the substrate W is easily released from the elastic film 138. At the same time, with the back film 139, scratch on the substrate ringing surface is prevented.

[Pressing Mechanism]

The pressing mechanism comprises the lid body 131 which is connected to a driving mechanism (not shown), a first airbag 132, the second airbag 133, the first pressure disk 134, the second pressure disk 135, the top ring 136, the elastic body 137, and the elastic film 138. Further, in an inner space formed by the lid body 131, the top ring 136, and the elastic body 137, the first airbag 132, the second airbag 133, the first pressure disk 134, the second pressure disk 135, and the elastic body 137 are respectively disposed at predetermined positions.

The lid body 131 comprises a lid part formed in an angular shape, a portion formed in a ring shape such that each of a central axis matches with each other near the center of an upper bottom surface side of the lid part, and a portion formed in a ring shape such that each of a central axis matches with each other near an outer peripheral of a lower bottom surface side of the lid part. The portion formed in the ring shape on the upper bottom surface side is connected to a driving mechanism (not shown). Further, the arm AM with the drive pin D1 is disposed at the portion formed in the ring shape on the lower bottom surface side.

The first pressure disk 134 is a cylindrical body in which the portion near the center of its lower bottom surface is formed in a cross section of a piece shape which is convex-shaped toward the elastic body 137. As shown in FIG. 3, the drive pins D2 disposed on the first pressure disk 134 are respectively inserted into the drive pin groove G2 provided on the second pressure disk 135. In this manner, the first pressure disk 134 and the second pressure disk 135 are vertically movably connected. Further, the first pressure disk 134 which is in a state that the drive pin D2 is inserted into the drive pin groove G2, smoothly moves up or moves down in accordance with the quantity of the pressure fluid sealed in the first airbag 132. It is noted that the lower bottom surface of the first pressure disk 134 may be formed in a shape in which the pressing force corresponding to the surface profile of the surface to be polished is applied to the substrate W through the elastic body 137. For example, in addition to forming in the cross section of the piece shape as shown in FIG. 3, the lower bottom surface of the first pressure disk 134 may be formed in a hemispherical shape.

The second pressure disk 135 is an annular body in which the portion near the outer peripheral of the lower bottom surface is formed in a cross section of a reversely concave shape which is convex-shaped toward the elastic body 137. As shown in FIG. 3, the drive pins D3 disposed on the second pressure disk 135 are respectively inserted into the drive pin groove G3 provided on the top ring 136. In this manner, the second pressure disk 135 and the top ring 136 are vertically movably connected. Further, the second pressure disk 135, which is in a state that the drive pin D3 is inserted into the drive pin groove G3, smoothly moves up or moves down in accordance with the quantity of the pressure fluid sealed in the second airbag 132. It is noted that the lower bottom surface of the second pressure disk 135 may be formed in a shape in which the pressing force corresponding to the surface profile of the surface to be polished is applied to the substrate W through the elastic body 137. For example, in addition to forming in the cross section of the concave conic shape as shown in FIG. 3, the lower bottom surface of the second pressure disk 135 may be formed in a concave hemispherical shape.

The top ring 136 is formed in a ring shape with an outer peripheral size which is the same as the outer peripheral size of the lid body 131. As shown in FIG. 3, the arms AM with the drive pin D1 are respectively inserted into the drive pin groove G1 provided on the top ring 136. In this manner, the lid body 131 and the top ring 136 are vertically movably connected.

The elastic body 137 is a low elastic body which is formed by a material with low elasticity and low repulsion such as polyurethane rubber, silicon rubber etc. For example, the elastic body 137 is a sponge which is cylindrically-shaped by these materials. The pressing force of the first pressing body and the pressing force of the second pressing body are applied to the substrate W through the elastic body 137. For example, in a conventional manner through which the pressing power is applied not through the elastic body 137, pressure of equal shape could only be applied to the substrate W. It means that with the configuration through which the pressing force is applied to the substrate W through the elastic body 137, the lower bottom surface of the first pressure disk 134 and the lower bottom surface of the second pressure disk 135 can respectively be formed in arbitrary shapes. This allows application of the pressing force of pressing force distribution corresponding to the surface profile of the surface to be polished. It is noted that, to prevent roll off, the lower bottom surface of the elastic body 137 (a surface which comes into contact with the inner bottom surface of the elastic film 138) is formed in a size which is smaller than the outer peripheral end of the substrate W. In the following, this is described in detail.

[Roll-Off]

Generally, a buffer part called chamfer is formed on the outer peripheral end of the substrate W. When receiving an impact from the outside, the chamfer part is broken to absorb the impact for preventing the entire substrate W from being destroyed, which is benefit of the chamfer part. On the other hand, a start point of the chamfer part forms an angle with the polishing pad 12. As it extends to the outer peripheral end from a corner of the angle, the chamfer part forms non-contacting portion with the polishing pad 12. Thereby, even the pressing force is generally uniformly applied to the substrate W, as it gets closer to the chamfer part, stress applied to the surface to be polished is increased by hertz stress theory. The stress becomes the highest at the start point of the chamfer part. Due to the change of the stress, excessive polishing is caused, which results in roll-off.

Then, as shown in FIG. 3, the size of the lower bottom surface of the elastic body 137 is formed in a size such that its outer peripheral end is positioned on more inner peripheral side than the chamfer part of the substrate W. That is, the size of the portion of the elastic film 138 which presses the substrate W (hereinafter referred to as pressing surface) is smaller than the diameter of the surface to be polished of the substrate W by a predetermined size, which is defined by the outer peripheral end of the substrate W and the chamfer part.

The predetermined size is called wafer over hung (OH). The pressing force is applied through the pressing surface of the elastic film 138 to the substrate W. Due to this, the pressing force is not applied to a portion where reaches the inner peripheral side by OH from the outer peripheral end of the substrate W. On the other hand, the outer peripheral end of the surface to be polished is slidably brought into contact with the polishing pad 12 at the outer side, as compared to the vertically downward position of the outer peripheral end of the pressing surface. Thereby, the pressing force diffuses and propagates in the substrate W so that the stress applied to the surface to be polished becomes generally uniform from the center part to the start point of the chamfer part (diffusion and propagation of hertz stress). Due to this, the roll off can be prevented.

Back to the description of FIG. 3, the elastic film 138 is an elastic cylindrical body which is cylindrically-shaped (copper type) with an inner diameter size capable of being fit on an outer peripheral surface of the top ring 136. Further, the elastic film 138 is formed of rubber material having good strength and durability such as ethylene propylene rubber (EPDM), polyurethane rubber, silicon rubber etc. It is noted that the elastic film 138 is also referred to as membrane. The elastic body 137 is disposed inside the elastic film 138 such that the respective central axes match with each other. Further, the inner peripheral surface of the elastic film 138 is closely contacted with the outer peripheral surface of the top ring 136. Due to this, the elastic film 138 is held by the top ring 136.

As mentioned, in the pressing mechanism of the polishing head 13, in response to the pressing force generated in the first air bag 132, the first pressure disk 134 presses the elastic body 137. Also, in response to the pressing force generated in the second air bag 133, the second pressure disk 135 presses the elastic body 137. Then, the pressing force of the pressing force distribution respectively corresponding to the shape of the lower bottom surface of the first pressure disk 134 and the shape of the lower bottom surface of the second pressure disk 135 is applied to the substrate W from the elastic film 138 through the elastic body 137.

[Torque Transmission Mechanism]

Further, at the time of polishing processing, in response to the rotation force from a driving mechanism (not shown), rotation force (torque) is applied to rotate the substrate W to which the pressing force is being applied. For example, in case of rotating the substrate W only by single system, through which the rotation force is transmitted from the lid body 131 to the top ring 136 and from the top ring 136 to the elastic film 138, buckling twist is caused on the pressing surface of the elastic film 138. As a result, sometimes, “wrinkle” is caused. Due to influence of the “wrinkle” caused on the pressing surface, the pressing force applied to the substrate W becomes non-uniform, resulting in deteriorating the polishing flatness of the surface to be polished. This is described using FIGS. 4A and 4B.

FIG. 4A shows the elastic film after rotating the substrate W only by the single system as mentioned and performing the polishing processing. As shown in FIG. 4A, the buckling twist is caused on the pressing surface of the elastic film 138. It is obvious that, as a result, the “wrinkle” is caused. Turbine blade mark (Tbm) shown in FIG. 4A represents the “wrinkle” caused on the pressing surface of the elastic film 138. FIG. 4B is a diagram schematically representing an analysis result of the buckling twist caused on the pressing surface of the elastic film 138. As is obvious from FIGS. 4A and 4B, when rotating the substrate W only by the single system, the buckling twist may be caused on the pressing surface of the elastic film 138.

Contrary to this, the torque transmission mechanism of the polishing head 13 has a first transmission system, through which the rotation force transmitted to the lid body 131 is transmitted from the top ring 136 to the elastic film 138. In addition, the torque transmission mechanism has a second transmission system, through which the rotation force is transmitted to the second pressure disk 135 through the drive pin D3 inserted into the drive pin groove G3 and is further transmitted to the first pressure disk 134 through the drive pin D2 inserted into the drive pin groove G2. The first pressure disk 134 and the second pressure disk 135 are respectively pressing the elastic body 137 so that the rotation force from the second transmission system is transmitted to the elastic body 137. The rotation force is further transmitted to the elastic film 138 by a coefficient of friction between the elastic body 137 and the elastic film 138. It means that each of the top ring 136, the first pressure disk 134, the second pressure disk 135, and the elastic film 138 moves or rotates according to the rotation of the lid body 131. The rotation force for rotating the substrate W is caused by friction force with the elastic film 138 to which the rotation force is applied from each of the first transmission system and the second transmission system. Thereby, the influence of the buckling twist is suppressed on the pressing surface part, which prevents the “wrinkle” from being caused on the pressing surface.

Next, a description is provided with regard to the pressing force applied to the substrate W. When performing polishing processing on the substrate W, the control unit 20 controls such that predetermined quantity of pressure fluid is respectively supplied to the first airbag 132 and the second airbag 133. Here, FIG. 5A shows a configuration example of a general polishing head which does not use the polishing head 13 of the present embodiment. With FIG. 5B, the distribution of the pressing force applied to the substrate W in this case is explained.

The polishing head shown in FIG. 5A flows air, which is the pressure fluid, toward the inside space formed by the polishing head and the elastic film to apply the pressing force to the substrate W in accordance with the quantity of the pressure fluid. As shown in FIG. 5B, with the polishing head, pressing force P is to be uniformly applied to the substrate W in principle. Further, as shown in FIG. 5B, at the time of polishing processing, rotation force V1 from the polishing pad (polishing table) and automatic driving force of the polishing head V2 act on the substrate W and the elastic film. As a result, (1) due to V2, “buckling twist” is caused on the elastic film, and (2) due to buckling phenomena of wafer by V1, omega-shape is caused. Due to the influence of (1) and (2), the pressing force in the pressing surface may become non-uniform. Thereby, the surface to be polished of the substrate W is formed in the omega shape and in a twisted disturbance shape. In the following, this is described in detail.

FIGS. 6A to 6B are diagrams explaining that in the polishing processing using the general polishing head, the surface to be polished of the substrate W is formed in the omega shape. Even being energized by the rotation force of the polishing table 11 (V1), by the retainer ring, the substrate W at the time of polishing processing is controlled its popping out toward an outer peripheral direction. Here, an area of the surface to be polished is “A”, the pressing force is “P”, a coefficient of friction between the wafer and the polishing pad is “μ” and in-plane force based on relation of A, P and μ is “F”. Then, following acts on the substrate W whose popping out is controlled; F=A*P*μ. Thereby, as shown in FIG. 6A, “buckling deflection” which moves toward the polishing pad side is caused on the substrate W to which the pressing force P is applied. As a result, as compared to other portions of the surface to be polished, the amount to be polished is increased on a portion of the surface to be polished of the substrate W where caused the deflection (convex portion).

FIG. 6B schematically shows a state of a moment in a case where the substrate W is polished in a state shown in FIG. 6A. It is obvious that the surface to be polished on the right side viewed from the front is polished in a concave shape (excessively polished). However, in the actual polishing processing, the substrate W is rotating. As a result, as shown in FIG. 6C, the surface to be polished of the substrate W will eventually be formed in the omega shape. It is noted that, in FIG. 6C, the surface to be polished of the substrate W is directed downward so that the surface to be polished after the polishing processing in an inverted omega shape. As mentioned, in the polishing processing using the conventional general polishing head, due to the pressing force P applied to the rear surface side of the surface to be polished of the substrate W, the rotation force of the polishing table, and reaction action in the retainer ring, its surface to be polished tends to be formed in the omega shape.

FIGS. 7A and 7B are diagrams for explaining the distribution of the pressing force by the polishing head 13 according to the present embodiment. FIG. 7A is a schematic diagram showing the distribution of the pressing force P which prevents the surface to be polished of the substrate W from being omega-shaped. It is noted that the strength of the pressing force P3 is represented by length of an arrow line. For example, if the length of the arrow line is relatively long, relatively strong pressing force is to be applied. Unlike the flat distribution of the pressing force P shown in FIG. 5B, the pressing force P shown in FIG. 7A is distributed in polygonal shape. This enables to apply the pressing force with different strength corresponding to the portion of the rear surface side of the surface to be polished of the substrate W. By applying the pressing force P shown in FIG. 7A to the rear surface side of the surface to be polished of the substrate W, the concave/convex portions on the surface to be polished of the omega shape shown by a dot line in FIG. 7A are respectively cancelled out. As a result, the shape of the surface to be polished will be brought closer to a desired shape shown by a solid line in FIG. 7A. With the polishing head 13 of the present embodiment, the polishing force P applied to the back surface side of the surface to be polished of the substrate W is controlled to achieve the distribution state shown in FIG. 7A.

FIG. 7B shows the distribution of the pressing force in the pressing head 13. Pressing force P1 generated by the pressure fluid sealed in the first airbag 132 is transmitted to the first pressure disk 134, and is applied as pressing force P3 to the rear surface side of the surface to be polished of the substrate W from the first pressure disk 134 through the elastic body 137. Further, pressing force P2 generated by the pressure fluid sealed in the second airbag 133 is transmitted to the second pressure disk 135, and is applied as pressing force P3 to the rear surface side of the surface to be polished of the substrate W from the second pressure disk 135 through the elastic body 137. It is noted that the strength of the pressing force P3 is represented by the length of an arrow line. For example, if the length of the arrow line is relatively long, relatively strong pressing force is to be applied.

As shown in FIG. 7B, with regard to a shape of a contact surface of the first pressure disk 134 which comes into contact with the elastic body 137, a portion near the center thereof is convex-shaped toward the elastic body 137. Thereby, the elastic body 137 is strongly pressed near the center portion of the first pressure disk 134 so that the pressing force is relatively strong, whereas in the portion near the outer peripheral of the first pressure disk 134, the pressing force is relatively weak. As a result, the pressing force P3 applied to the rear surface side of the surface to be polished of the substrate W is distributed as shown in FIG. 7B. Further, as shown in FIG. 7B, a shape of a contact surface of the second pressure disk 135 which comes into contact with the elastic body 137 is formed in a concave shape. Thereby, the elastic body 137 is strongly pressed near the outer peripheral end of the second pressure disk 135 so that the pressing force is relatively strong, whereas in the portion near the inner peripheral end of the second pressure disk 135, the pressing force is relatively weak. As a result, the pressing force P3 applied to the rear surface side of the surface to be polished of the substrate W is continuously distributed as shown in FIG. 7B. It means that, by applying the pressing force corresponding to the surface profile of the surface to be polished on the substrate W in the continuously distributed state, it is possible to prevent the surface to be polished from being omega-shaped.

FIGS. 8A to 8C are diagrams explaining connection of the lid body 131 and the top ring 136 through the drive pin D1. FIG. 8A schematically shows a case in which the lid body 131 and the top ring 136 are connected at a higher position compared with the case shown in FIG. 3. Provided that torque is transmitted at a position of height H from the polishing pad surface (torque transmission position). With an outer bottom surface end portion of the top ring 136 as fulcrum and a position of the drive pin D1 which drives automatic rotation of the polishing head and which gives rotational reaction from the polishing table as point of action, force of moment M acts on the polishing table. In addition, it is influenced by vibration phenomenon (stick slip phenomenon) generated on the polishing surface (slide surface). Thereby, in a case where the lid body 131 and the top ring 136 are connected at relatively high position, as shown in FIG. 8B, a phenomenon, by which the end portion of the center side of the polishing table of the top ring 136 floats, is caused. Thereby, as shown in FIG. 8B, the pressing force is not applied to the end portion of the substrate W, which makes it impossible to enhance the polishing flatness near the end portion of the substrate W. To avoid the occurrence of the floating phenomenon, in the polishing head 13 of the present embodiment, as shown in FIG. 3, it is configured such that a connection position H of the lid body 131 and the top ring 136 through the drive pin D1 is at a low position. As compared to the polishing head shown in FIG. 8A, the polishing head 13 of the present embodiment having the connection position at relatively low position, occurrence of the floating phenomenon is suppressed. Thereby, the polishing flatness of the end portion of the substrate W can be enhanced.

FIGS. 9A and 9B are diagrams for explaining that the polishing flatness of the end portion of the substrate W changes by the difference of how the elastic film is adhered and fixed. FIG. 9A shows a diagram schematically showing an elastic film adhered on the general polishing head, not on the polishing head 13 of the present embodiment. The elastic film shown in FIG. 9A is fitted on the outer peripheral surface of the polishing head top ring. An adhesive surface is a portion of the outer peripheral surface and a portion of the lower bottom surface of the top ring. For example, in a case where the “floating” phenomenon as mentioned is caused to the polishing head, starting from the outer peripheral end portion of the lower bottom surface of the polishing head, the elastic film is lifted in an upward direction. In this case, the shortest distance between the end portion of the substrate and a fixed end of the elastic film in terms of strength of material is defined as clearance L1. FIG. 9B shows a state in which the elastic film 138 is adhered in the polishing head 13 of the present embodiment. The elastic film 138 shown in FIG. 9B is fitted on the outer peripheral surface of the top ring 136. Only the portion of the outer peripheral surface of the top ring 136 which comes into contact with the elastic film 138 is adhered. In this state, in a case where the “floating” phenomenon as mentioned is caused to the top ring 136, starting from the outer peripheral side end portion of the lower bottom surface of the polishing head, the elastic film is lifted in an upward direction. The distance between a fixed end in terms of strength of material and the end portion of the substrate W is defined as clearance L2.

Description is provided, for example, in a case where the “floating” phenomenon of the same height is caused. When comparing a state of clearance L1 as shown in FIG. 9A with a state of clearance L2 as shown in FIG. 9B, by a strength of material theory, the one having longer distance from the starting point to the end portion of the substrate W experiences less change of the pressing force to the end portion of the substrate W. It means that, with adoption of the configuration of the polishing head 13 of the present embodiment as shown in FIG. 9B, even the “floating” phenomenon is caused to the top ring 136, reduction of the polishing flatness of the end portion of the substrate W can be reduced. In other words, it can be said that the polishing head 13 of the present embodiment can reduce the change of the load transmission efficiency to the end portion of the substrate W. In the following, with reference to FIGS. 10 and 11, a description is provided with regard to the verification result in which influence on the flatness of the end portion of the substrate by the difference of how the elastic film is fixed to the top ring 136 (adhered and fixed state) is verified.

FIGS. 10A, B, and C are diagrams showing the combination of the top rings respectively having different shapes of the adhesive surface and the retainer rings respectively having different shapes. FIGS. 10D, E, and F are diagrams showing measurement result of cross-sectional shapes (A, B, C) of the substrate W and gradients of the end portion of the substrate W (A, B, C) in a case where the polishing processing is performed in the respective combination. It is noted that the substrate W has a diameter of 300 [mm]. The size of a longitudinal axis of the shape is 100 [nm/div]. Further, in the polishing processing in which the polishing processing is performed in the respective combination as shown in FIGS. 10A to 10F, the rotation force is to be transmitted to the substrate W only by the first transmission system as mentioned.

An adhesive surface of the top ring 136 a and the elastic film 138 as shown in FIG. 10A is a portion of an outer peripheral surface of the top ring 136 a and a portion of a lower bottom surface of the elastic film 138. A cross-sectional shape A as shown in FIG. 10D represents the cross-sectional shape of the substrate W when the polishing processing is performed under this condition. It is obvious that a portion near the center of the substrate W is affected by the “bucking twist”. Further, the cross-sectional shape A obviously shows that the polishing surface is asymmetric. To reduce an area of the adhesive surface with the elastic film 138 as compared to the top ring 136 a, the top ring 136 b as shown in FIG. 10B is formed such that the inner peripheral side of the lower bottom surface of the top ring 136 b does not come into contact with the elastic film 138. A cross-sectional shape B as shown in FIG. 10E represents the cross-sectional shape of the substrate W when the polishing processing is performed under this condition. It is obvious, even in this case, that a portion near the center of the substrate W is affected by the “bucking twist”. Further, the cross-sectional shape B obviously shows that the polishing surface is asymmetric. To reduce an area which comes into contact with the polishing pad 12 as compared to the retainer ring 140, a retainer ring 140 c as shown in FIG. 10C is formed such that the outer peripheral side of the lower bottom surface of the retainer ring 140 c does not come into contact with the polishing pad. A cross-sectional shape C as shown in FIG. 10F represents the cross-sectional shape of the substrate W when the polishing processing is performed under this condition. It is obvious, even in this case, that a portion near the center of the substrate W is affected by the “bucking twist”. Further, the cross-sectional shape C obviously shows that the polishing surface is asymmetric.

FIG. 11A is a diagram showing a combination of the top ring 136 and the retainer ring 140 according to the present embodiment. FIG. 11B is a diagram showing measurement result of a cross-sectional shape D of the substrate W and a gradient D of the end portion of the substrate W when performing the polishing processing in this combination. FIG. 11C is a diagram for comparing the gradients (A, B, C) in the respective combinations as shown in FIGS. 10A to 10F and the gradient D as shown in FIG. 11. It is noted that, in the polishing processing in which the polishing processing is performed in the respective combination shown in FIGS. 11A to 11C, the rotation force is to be transmitted to the substrate W by the first transmission system and the second transmission system as mentioned.

FIG. 11A shows how the top ring 136 is adhered and fixed to the elastic film 138, in which the portion of the outer peripheral surface of the top ring 136 is adhered to the portion of the inner peripheral surface of the elastic film 138. A cross-sectional shape D as shown in FIG. 11B represents the cross-sectional shape of the substrate W when the polishing processing is performed under this condition. A portion near the center of the substrate W is not affected by the “bucking twist”. It is obvious that it has good bilateral symmetry. Further, as shown in FIG. 11C, inclination angles from the gradient A to the gradient D are compared. It is obvious, in a state shown in FIG. 11A, in which the portion of the outer peripheral surface of the top ring 136 is adhered to the portion of the inner peripheral surface of the elastic film 138, that “rising” of the outer peripheral portion of the substrate is effectively suppressed.

[Control Procedure for Polishing Processing]

Next, a description is provided with regard to a procedure of the polishing processing using the polishing processing device 1 of the present embodiment. FIG. 12 is a diagram explaining main control procedure controlled by the control unit 20 when performing the polishing processing method. In response to receiving an input of an instruction to start by an operator of the polishing processing device 1, the control unit 20 starts to control (Step S100). After performing predetermined initial processing, the control unit 20 causes a substrate carrying means (not shown) to carry in the substrate W to cause the holding mechanism of the polishing head 13 to hold the substrate W (Step S101). The control unit 20 gives an instruction to the fluid supply mechanism such that predetermined quantity of pressure fluid is respectively supplied to the first airbag 132 and the second airbag 133 from the air pipe AP to apply the pressing force toward the substrate W and the polishing pad 12 (Step S102).

Further, the control unit 20 confirms whether appropriate pressing force is applied to the substrate W or not through a sensor part (not shown). If it is confirmed that the pressing force is appropriate (Step S103: Y), the control unit 20 gives an instruction to a motor (not shown) to start rotating the polishing table 11 and the polishing head 13 (Step S104). Due to this, the polishing table 11 and the polishing head 13 start rotating horizontally.

After instructing to start rotating the polishing table 11 and the polishing head 13, the control unit 20 instructs to position the nozzle N and gives an instruction to the polishing solution supply mechanism to start supplying the polishing solution (Step S105). Due to this, the polishing solution is supplied from the nozzle N toward the polishing surface of the polishing pad 12. After instructing to start supplying the polishing solution, when detecting that specified polishing time has lapsed by a timer (not shown) (Step 106: Y), the control unit 20 gives an instruction to the polishing solution supply mechanism to stop supplying the polishing solution (Step S107).

Thereafter, the control unit 20 gives a stop instruction to the motor to stop rotating the polishing table 11 and the polishing head 13 (Step S108). Also, the control unit 20 gives an instruction to a pressure fluid supply mechanism to recover the pressure fluid supplied (Step S109). Then, the control unit 20 causes a substrate carrying means (not shown) to carry out the substrate W. The polishing processing is completed in this manner.

As mentioned, with the polishing processing device 1 according to the present embodiment, the pressing force respectively corresponding to the shape of the lower bottom surface of the first pressure disk 134 and the shape of the lower bottom surface of the second pressure disk 135 can be applied to the substrate W from the elastic film 138 through the elastic body 137. Due to this, desired pressing force (P3) can be applied over the entire surface of the surface to be polished of the substrate W without any discontinuous part. This enables to prevent the surface to be polished of the substrate W from being omega-shaped, which was impossible in a conventional pressure-equalized pattern. This also enables to enhance GBIR and SFQR of the substrate surface.

Further, with the configuration through which the pressing force is applied to the substrate W through the elastic body 137, it is possible to respectively form the lower bottom surface of the first pressure disk 134 and the lower bottom surface of the second pressure disk 135 in the arbitral shapes. Thereby, it is possible to apply the pressing force to the substrate W with the distribution corresponding to the surface profile of the surface to be polished. This prevents the surface to be polished of the substrate W from being formed in the omega shape. This also enables to enhance GBIR and SFQR of the substrate surface. It is noted that the description has been provided in a case where two pressure disks are used (the first pressure disk 134 and the second pressure disk 135). To achieve intended flatness accuracy of the substrate, multiple number of disks may be used.

Further, the rotation force for rotating the substrate W is applied from the first transmission system and the second transmission system respectively. Due to this, occurrence of twisted disturbance is suppressed on the pressing surface. This prevents excess or deficiency of the pressing force in the pressing surface.

Further, the lower bottom surface of the elastic body 137 is formed in a size smaller than the outer peripheral end of the substrate W. Due to this, the pressing surface of the elastic film 138 presses the substrate W in the inner peripheral side than the outer peripheral end of the substrate W. This prevents occurrence of “sagging” of the surface to be polished near the outer peripheral end of the substrate W. It means that the occurrence of excessive polishing (roll off) can be prevented. This enables to enhance GBIR and SFQR of the substrate surface.

Further, in the polishing processing device 1, the lid body 131 and the top ring 136 are connected through the drive pin D1 at a low position. This prevents occurrence of floating of the polishing head 13, which enables to enhance the polishing accuracy of the end portion of the substrate W. This enables to enhance GBIR and SFQR of the substrate surface.

Second Embodiment

In the present embodiment, a description is provided with regard to an example in which a side of the elastic film has a bellows structure. It is noted that, with regard to the portions which are identical to those of the polishing processing device 1 and the polishing head 13 described in the first embodiment, the same reference numerals are attached and the descriptions thereof are omitted.

FIG. 13A is a diagram showing one configuration example of a polishing head according to the present embodiment. The polishing head of the present embodiment is different from the polishing head 13 of the first embodiment in that (1) it comprises an elastic film 238 with bellows-shaped side, and (2) the back film 139 and the retainer ring 140 are separated from each other. The back film 139 shown in FIG. 13A is adhered on an outer bottom surface of the elastic film 238 independently of the retainer ring 140. Further, as shown in FIG. 13A, one end of the side of the bellows structure of the elastic film 238 is connected to the retainer ring 140. With expansion and contraction of the bellows portion in accordance with the pressing force received, the pressing surface of the elastic film 238 as connected in this manner can move up or move down horizontally.

FIG. 13B is a schematic diagram showing how the elastic film 138 and the retainer ring 140 are connected in the pressing mechanism of the first embodiment. When the pressing force P is uniformly applied to the inner bottom surface of the elastic film 138 in this state, as shown by a smooth curve of a dotted line in FIG. 13B, polishing pressure near the connecting portion with the retainer ring 140 is relatively low whereas the polishing pressure near the center of the elastic film 138 is relatively high. It means that transmission loss is caused to the polishing pressure which is transmitted to the rear surface side of the substrate W for every portion of the elastic film 138.

FIG. 13C is a schematic diagram of a case where the pressing force P is uniformly applied to an inner bottom surface of the elastic film 238 according to the present embodiment. When the pressing force P is uniformly applied to the inner bottom surface of the elastic film 238 in this state, as shown by a dot line in FIG. 13C, due to the bellows structure of the elastic film 238, its pressing surface moves down horizontally and the pressing force P is applied to the rear surface side of the substrate W. It means that with adoption of the bellows structure, the pressing force applied to the inner surface side of the elastic film 238 can be applied to the rear surface side of the substrate W without any loss. Further, even in a case where the “floating phenomenon” as described in FIG. 8 occurs, in terms of strength of material theory, the polishing pressure is to be transmitted to the substrate W without any loss.

As mentioned, in the polishing processing device 1 according to the present embodiment, with expansion and contraction of the bellows portion of the elastic film 238, the pressing surface moves up or moves down horizontally. This enables to effectively transmit the polishing pressure to the substrate W without any loss. Further, it is possible to apply the pressing force to the rear surface side of the substrate W without any loss with continuous distribution corresponding to the surface profile of the surface to be polished through the elastic body 137. Further, with the torque mechanism comprising of the first transmission system and the second transmission system as mentioned, it is possible to further suppress the occurrence of the buckling twist. This enables to prevent the surface to be polished of the substrate W from being formed in the omega shape. Also, due to this, GBIR and SFQR of the substrate surface can be enhanced.

The above embodiments are only the examples to specifically explain the present invention. Therefore, the scope of the invention is not limited to these embodiments. 

1. A polishing head to be provided in a polishing processing device having a polishing surface which horizontally rotates, comprising: a holding unit configured to hold a substrate to be subjected to polishing processing in such a manner that a surface to be polished of the substrate is slidably brought into contact with the polishing surface; and a pressing unit configured to press the substrate held by the holding unit from a rear surface side of the surface to be polished toward the polishing surface, wherein the pressing unit comprises a pressing body, an elastic body disposed to come into contact with the pressing body, and a fluid supply unit configured to supply the pressure fluid to the pressing body, wherein the pressing body is configured such that pressure fluid is sealed to the pressing body to generate pressing force in accordance with quantity of the pressure fluid toward the rear surface side of the substrate, wherein the pressing body comprises a first pressing body which is cylindrically-shaped and a second pressing body which is annularly-shaped disposed to surround the first pressing body, wherein the first pressing body is formed so that a portion near a center of a contact surface which comes into contact with the elastic body is convex-shaped toward the elastic body side, and the second pressing body is formed so that a portion which is outer peripheral side of the contact surface which comes into contact with the elastic body is convex-shaped toward the elastic body side, and wherein the pressing force, generated by the pressure fluid sealed in the first pressing body and the second pressing body separately and respectively, is respectively applied to the rear surface side of the substrate held by the holding unit through the elastic body.
 2. The polishing head according to claim 1 further comprises a driving unit for horizontally rotating the holding unit, wherein the second pressing body is connected to move according to the holding unit, wherein the first pressing body is connected to move according to the second pressing body, and wherein the first pressing body and the second pressing body are respectively connected to connection destinations vertically movably such that the respective pressing force applied to the rear surface side of the substrate changes before and during horizontal rotation.
 3. The polishing head according to claim, wherein the pressing unit further comprising: an elastic cylindrical body, an inner bottom surface of which comes into contact with the elastic body, and an outer bottom surface of which comes into contact with the rear surface side of the substrate; and a top ring disposed between an inner peripheral surface of the elastic cylindrical body and an outer peripheral surface of the elastic body and holds the elastic cylindrical body, wherein the top ring is connected to move according to the holding unit.
 4. The polishing head according to claim 3, wherein the holding unit is configured to connect to the top ring at a position at which floating of the elastic cylindrical body from the substrate is suppressed.
 5. The polishing head according to claim 3, wherein the outer peripheral surface of the top ring is brought into close contact with the inner peripheral surface of the elastic cylindrical body to hold the elastic cylindrical body, thereby the elastic cylindrical body moves according to the top ring.
 6. The polishing head according to claim 1, wherein the pressing body comprises an airbag in which the pressure fluid is sealed to expand and generates pressing force in accordance with quantity of the pressure fluid.
 7. The polishing head according to claim 1, wherein a size of a surface of the elastic body, which applies the pressing force from the rear surface side of the surface to be polished, is smaller than a size of the surface to be polished.
 8. The polishing head according to claim 3, wherein a side of the elastic cylindrical body is formed in a bellows shape and one end of the side formed in the bellows shape is held by the top ring, and with expansion and contraction of the side formed in the bellows shape starting from one end of the side held by the top ring, an outer bottom surface of the elastic cylindrical body which comes into contact with the rear surface of the substrate horizontally moves up or moves down corresponding to the pressing force.
 9. A polishing processing device comprising: a polishing table having a circular or generally circular polishing surface, a polishing head configured to hold a substrate to be subjected to polishing processing to slidably bring a circular surface to be polished of the substrate into contact with the polishing surface, and a driving unit configured to horizontally rotate at least one of the polishing head and the polishing table, wherein the polishing table is configured such that a radius of the polishing surface is larger than a diameter of the surface to be polished of the substrate, wherein the polishing head comprises: a holding unit configured to hold the surface to be polished of the substrate to be slidably brought into contact with the polishing surface, a pressing body, in which pressure fluid is sealed to generate pressing force in accordance with quantity of the pressure fluid toward the rear surface side of the substrate, an elastic body disposed to come into contact with the pressing body, and a fluid supply unit configured to supply pressure fluid to the pressing body, wherein the pressing body comprises a first pressing body which is cylindrically-shaped and a second pressing body which is annularly-shaped disposed to surround the first pressing body, wherein the first pressing body is formed so that a portion near a center of a contact surface which comes into contact with the elastic body is convex-shaped toward the elastic body, wherein the second pressing body is formed so that a portion which is outer peripheral side of the contact surface which comes into contact with the elastic body is convex-shaped toward the elastic body side, and a pressing unit configured to respectively apply the pressing force, generated by the pressure fluid sealed in the first pressing body and the second pressing body separately and respectively, to the rear surface side of the substrate held by the holding unit through the elastic body. 